The study utilizes two different stable isotopes of calcium to determine calcium kinetics. The fact that the isotopes are non-radioactive, they can be used in children and pregnant women. One isotope is given intravenously, the other by mouth. Since the isotopes have different atomic weights the two calciums can be determined in the mass spectrometer simultaneously. Blood sampling is required for 12 hours only. Urine collections are made continuously every 8 hours for 2 weeks. Using the modeling program designed by Dr. Mones Berman, one can determine the size of the several calcium pools. Another component of the study involves patients with the Prader-Willi syndrome (PWS) and patients with simple exogenous obesity as controls. The PWS patients and obese control children were given loading tests with cornstarch vs cooked corn, rice starch vs cooked rice, and potato starch vs cooked potato. These tests will be repeated in these same individuals as they lose weight toward normal. The glucose and insulin responses are followed. The results on these patients will also be compared with those obtained in glycogen storage disease patients who lack the whole control loop of blood glucose regulation. It is much more difficult to interpret the data from obese individuals than in those with glycogen storage disease. Obese individuals who have a diabetic GTT do have a readily recognizable abnormal starch tolerance test.